As is known from the technical field of cutting up structures, including subsea structures, of the kinds indicated above, use is made of cutting machines fitted with wires containing suitable cutting parts, such as so-called diamond wires. One of these cutting machines is disclosed in patent EP 0540834 B2, belonging to the proprietor of the present application. That machine comprises a diamond wire running around two pulleys positioned on slides able to move in an essentially horizontal direction along two suitable motion tracks. That machine, by means of the diamond wire, cuts the legs of for example a subsea structure in a single direction, generally horizontal and at right angles to the legs themselves.
As is also known, the supporting legs of a subsea structure, such as an oil platform standing on four legs fixed to the sea bed, must be cut one at a time. The cutting machine is therefore positioned appropriately on the first leg, and once it has cut the first leg it is transferred to another leg, and so on until it has cut all the legs of the structure at a certain height or depth. This leg cutting operation is very lengthy and must be carried out with the utmost safety and efficiency.
As mentioned above, each of the legs is cut in an essentially horizontal direction and therefore at right angles to the leg itself. This cut causes problems, because at the end of the cut the bottom part of each leg is still fixed to the sea bed while the top part is still connected to the supported structure but is disconnected and simply resting on the fixed bottom part. It could therefore slide against the latter, which would be highly undesirable. This risk of the top part of the leg sliding relative to the fixed bottom part is absolutely to be avoided as it could create serious problems of stability in the leg cutting operations, each of which legs, once cut, must be sufficiently stable, even with the top part simply resting on the bottom part fixed to the sea bed, to allow the remaining legs to be cut.